/*
 * Copyright 2002-2010 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace Spring.Util;

/// <summary>
/// Utility class containing helper methods for object comparison.
/// </summary>
/// <author>Aleksandar Seovic</author>
public class CompareUtils
{
    /// <summary>Compares two objects.</summary>
    /// <param name="first">First object.</param>
    /// <param name="second">Second object.</param>
    /// <returns>
    /// 0, if objects are equal;
    /// less than zero, if the first object is smaller than the second one;
    /// greater than zero, if the first object is greater than the second one.</returns>
    public static int Compare(object first, object second)
    {
        // anything is greater than null, unless both operands are null
        if (first == null)
        {
            return (second == null ? 0 : -1);
        }
        else if (second == null)
        {
            return 1;
        }

        if (!first.GetType().Equals(second.GetType()))
        {
            if (!CoerceTypes(ref first, ref second))
            {
                throw new ArgumentException("Cannot compare instances of ["
                                            + first.GetType().FullName
                                            + "] and ["
                                            + second.GetType().FullName
                                            + "] because they cannot be coerced to the same type.");
            }
        }

        if (first is IComparable)
        {
            return ((IComparable) first).CompareTo(second);
        }
        else
        {
            throw new ArgumentException("Cannot compare instances of the type ["
                                        + first.GetType().FullName
                                        + "] because it doesn't implement IComparable");
        }
    }

    private static bool CoerceTypes(ref object left, ref object right)
    {
        if (NumberUtils.IsNumber(left) && NumberUtils.IsNumber(right))
        {
            NumberUtils.CoerceTypes(ref right, ref left);
            return true;
        }

        return false;
    }
}
